Studies will be conducted to identify and investigate the biochemical and immunological factors of probable importance in the carcinogenesis of experimental neoplasms induced in animals by 5-nitrofurans and related nitro- and amino-aromatic and heterocyclic compounds. Utilizing certain 14C-labeled nitrofuran carcinogens, the isolation and characterization of metabolic adducts to fragments of DNA, RNA, or protein will be studied. Investigations of alterations of humoral and cellular immunologic characteristics of animals chronically administered carcinogenic and non-carcinogenic nitrofurans will be conducted. The pathogenesis and prevention of neoplastic formation in rats, mice, and hamsters by selected compounds will be studied. Investigations of dosage effects, differential species and strains susceptibility, and additional structure-activity carcinogenesis relationships will be conducted. The objectives of these studies are to define and describe the experimental conditions under which 5-nitrofuran compounds and chemically related derivatives act as chemical carcinogens, and to identify and modify those factors of seeming importance in the development of tumors induced by these chemicals.